In many telecommunication systems, communications networks are used to exchange messages among several interacting spatially-separated devices. Networks can be classified according to geographic scope, which could be, for example, a metropolitan area, a local area, or a personal area. Such networks can be designated respectively as a wide area network (WAN), metropolitan area network (MAN), local area network (LAN), or personal area network (PAN). Networks also differ according to the switching/routing technique used to interconnect the various network nodes and devices (e.g., circuit switching vs. packet switching), the type of physical media employed for transmission (e.g., wired vs. wireless), and the set of communication protocols used (e.g., Internet protocol suite, SONET (Synchronous Optical Networking), Ethernet, etc.).
Wireless networks are often preferred when the network elements are mobile and thus have dynamic connectivity needs, or if the network architecture is formed in an ad hoc, rather than fixed, topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in the radio, microwave, infrared, red, optical, etc. frequency bands. Wireless networks advantageously facilitate user mobility and rapid field deployment when compared to fixed wired networks.
As the volume and complexity of information communicated wirelessly between multiple devices continues to increase, overhead bandwidth required for physical layer control signals continues to increase at least linearly. The number of bits utilized to convey physical layer control information has become a significant portion of required overhead. Thus, with limited communication resources, it is desirable to reduce the number of bits required to convey this physical layer control information, especially as multiple types of traffic are concurrently sent from an access point to multiple terminals. For example, when a wireless device sends low-rate uplink communications to an access point, it is desirable to minimize the number of bits used for signaling and packet acquisition while maintaining backwards compatibility. Thus, there is a need for an improved protocol for mixed-rate transmissions.